This is a great solution for me, thanks. The app I'm running outputs log messages to the console, so I often just plug in a HDMI screen to see the status of the application on the RPi, but I don't connect a keyboard to it.

I just set those two lines to 0 (BLANK_TIME and POWERDOWN_TIME) and this worked great.
I am running Debian Wheezy (soft-float).

Only way I've been able to fix this issue is install xscreensaver. To install you need "sudo apt-get install xscreensaver" . In the gui you will now have the "screensaver" option under preferences. Here you can disable the blank screen. Let me know if this makes sense and helps!

3 Make the file run automatically every minute in cron by executing crontab -e and entering

* * * * * /home/pi/killOffScreensaver.sh > /dev/null

Very hacky and might not be safe but was quick and simple for me. For an explanation;

It prints the process tree (ps -ef), takes only lines with the phrase 'xscreensaver -no-splash' in (grep 'xscreensaver -no-splash'), then removes lines with the word grep in (as the grep process itself will appear), then takes characters 3-14 that contain the ID of the process (cut -c 3-14), then removes all white space using sed, then issues the kill command on the process ID).

I finally had success disabling blanking with the default Raspbian installation. The xset program is not installed by default, so I did the "sudo apt-get install x11-xserver-utils". I tested using the "xset q" command. To disable the screen blanking with the default LXDE, edit the file:
/etc/xdg/lxsession/LXDE/autostart
comment out a xscreensaver command, and add these xset lines

About 2 years ago Rasadmin may well have posted THE answer for your system. However, I vote for carlhage, because that solution worked for my late model Raspbian system (uname -r says '3.12.22+' with LXDE display manager). Don't put magic xset commands in /etc/rc.local as advised elsewhere. Use the magic @xset commands where carlhage says.

I am curious as to where all these obscure commands come from? Linux seems just so over whelming surely there must be documentation somewhere that explains these issues. I have tried the lightdm.conf , kdb and none of them have worked, The TV display blanks out after 10 mins. I start the GUI display which I assume is the X server via startx. It looks like the chap from France might have the fix for this.
Cheers Alan